Method of making an embossing structure

ABSTRACT

THE PRESENT INVENTION RELATES TO THE ART OF PRODUCING EMBOSSING PLATENS OR PLATES FROM PARENCHYMA, A WASTE PORTION OF BAGASSE. IT CONTEMPLATES THE EXTRACTION OR REMOVAL OF PARENCHYMA FROM THE FIBROUS PORTIONS OF THE BAGASSE, THE FORMATION OF COMPOSITIONS BY ADMIXTURE OF THE PARENCHYMA WITH THERMOSETTING BINDER RESINS, AND THE USE OF THE COMPOSITIONS AS MOLDING COMPOUNDS FOR FORMATION OF EMBOSSING PLATES OR STRUCTURES BY HOT STAMPING METHODS. THESE PLATES INCLUDING, ESPECIALLY, THOSE PROVIDING ANY DESIRED PATTERN INCLUDING, ESPECIALLY, THOSE PROVIDING WOOD GRAIN EFFECTS.

July 20, 1971 MACKINNON 3,594,244

METHOD OF MAKING AN EMBOSSING STRUCTURE Filed May 22, 1967 FIGURE 1 FIGURE 2 J. MACKINNON .l. RIONDA mvemoas H. F. SCHROEDER PATENT ATTORNEY United States Patent Office 3,594,244 Patented July 20, 1971 3,594,244 METHOD OF MAKING AN EMBOSSING STRUCTURE John Mackinnon, Edison, N.J., Jose A. Rionda, Beverley Hills, Jamaica, and Herbert F. Schroeder, South Plainfield, N.J., assignors to Esso Research and Engineering Company Filed May 22, 1967, Ser. No. 640,273 Int. Cl. 329i 5/00 U.S. Cl. 156-622 7 Claims ABSTRACT OF THE DISCLOSURE Bagasse, a by-product of sugar manufacture, is the dried, crushed residue of the sugar cane stalk. It consists principally of fibrous components and parenchyma from which the juice has been extracted. The latter is generally (and hereinafter) referred to as pith. The fibrous components include the rind fiber and the fibro-vascular fiber bundles or cells. The fibrous components, especially the fibro-vascular fiber bundles or shives, are united or bonded together with the pith, though some of the pith is found in the bagasse in loose powder form.

The pith is a nonorganized, nonfibrous, pulpy substance. Its chemical nature, light cellular structure and high surface area, relative to its mass, make it a highly reactive and absorbent material of limited commercial utility. It is, in fact, most often a waste product.

In prior art processes, the pith, which consistitutes a major proportion of the bagasse, is separated via chemical or mechanical means from the fibrous materials as completely as possible, and then discarded. This has been considered necessary to provide a raw material suitable for the formation of structural boards or finished products of optimum structure and quality-viz, optimum for machine operation, product quality and low chemical cost per ton of pulp produced. In the separation, large quantities of the fibre-vascular fiber are also unavoidably removed along with the pith, and generally discarded there with. This represents additional waste and, though bagasse is variable in composition, the waste can range above about 50 percent, based on the initial weight of the bagasse.

Nonetheless, as stated, bagasseboard made from the fibrous portions of the bagasse has become a stable article of commerce and it is often desirable to provide various textures or embossed surfaces on these and other board structures. Embossed surfaces on wood particleboard, bagasseboard and the like are currently commercially produced by the use of expensively machined, engraved or etched metal platens. These platens are capable of producing replicate boards with identically embossed surfaces, but the expense involved in the production of these plates mounts as design increases in complexity.

:The primary objective of the present invention is to obviate the foregoing and other prior art deficiencies while providing a novel process and new and useful structures made from the pith, or the conventional reject portion of the bagasse. In particular, this invention contemplates extraction or removal of the pith from the bagasse, and use of a portion of the pith to provide compositions useful for forming embossing platens that can produce virtually 5 any desired pattern. A further object is to provide a use for virtually the whole bagasse as useful articles of manu facture.

These and other objects are achieved in accordance with the present invention which contemplates the formation of compositions by extraction and removal of pith from bagasse, and admixture of the pith with thermosetting resins. The pith is extracted and separated from the whole bagasse by known chemical or mechanical means, preferably the latter, admixed with the desired amount of thermosetting resin, or resins, and then deliquefied or dried to provide a powder.

In forming the pith-resin compositions, the amount of resin applied to or admixed with the extracted pith depends to some extent upon the chemical nature and affinity of the pith for the particular resin. In general, from about 5 to about 50 percent resin is mixed with the pith, based on the weight relationship of dry pith to dry resin solids. Preferably from about 5 weight percent to about 30 Weight percent resin is applied to the pith.

The pith-resin compositions are formed by spraying or by admixture of solutions or dispersions of the resin with the pith, followed by removal of the liquid. It is necessary to deliquefy or dry the resultant composition by removing the liquid without curing the resin. Preferably, this is accomplished by quick partial deliquefication or drying at a temperature below the curing temperature of the resin. The maximum temperature to be used, and time of drying, thus depends upon the nature of the resin.

In most instances it is preferable to admix, spray or otherwise incorporate the pith and resin by addition of the resin to the pith, whether wet or dry, as a slurry or solution. Generally, from about percent to about 50 percent, and preferably from about percent to about percent, resin is dispersed in a liquid, e.g., water, based on the total weight of the liquid-solids system formed. A sutficient amount of the liquid is then removed to form a dry powder.

Essentially any thermosetting resin, plastic or plasticlike substance which will bind the pith and which, of course, can be cured or hardened, and permanently set by application of sufficient heat, can be used in this invention. Preferably, the thermosetting resin to be used is one having a viscosity ranging from about to about 1000 centipoises when the total solids content of the resin solution or slurry is about fifty percent. Illustrative of 'the more preferred thermosetting resins are phenol-alde- *hyde resins, particularly phenolformaldehyde and ureaformaldehyde resins whether used alone or with catalyst materials to aid in curing.

The dry powders are applied upon, sprinkled, or spread over the surfaces of the pattern to be copied. Generally from about 0.10 to about pounds per square foot, or more generally from about 0.15 to about 0.35 pound per square foot of powder is desirable to cover the pattern area. Both the pattern and powder are then prepressed cold at pressures ranging from about 200 to about 1000 pounds per square inch, or preferably from about 300 to about 750 pounds per square inch. Both pattern and powder composition are then pressed in a heated platen press to provide a final cured pitch-resin composition ranging from about V to about A, and more generally from about A to about Ms of the original thickness of the loose dry powder. In general, the finished pith-resin composition is pressed at temperatures ranging from about 250 F. to about 400 F. and preferably from about 275 F. to about 350 F. at a total press time ranging from about three to about eight minutes to provide a final composition thickness ranging from about 5, inch to about inch.

The pattern and pressed pith-resin composition are then removed from the press and the pattern is separated from the composition. The pitch-resin composition in then secured to a back-up plate or support to form the embossing platen.

The nature and the process of forming these novel structures will be better understood by reference to the attached figures and to the following detailed description which makes reference to the figures, wherein:

FIG. 1 provides a cross-sectional schematic view illustrating the several steps involved in the preparation of the finished or cured pitch-resin composition, embossing structure or printing member used in forming the embossing platen; and

FIG. 2 provides a side view of a finished platen which includes an embossing or printing member and a supporting plate.

Referring to FIG. 1 is shown a mold or matrix 10 provided with a pattern 11, a negative of which is to be reproduced upon an embossing structure or printing member 14 to form the face of a platen.

The step for construction of the platen include:

(a) Covering, e.g., by spraying or wiping, the surface of the mold or matrix 10, which contains the pattern 11 to be copied, with a low surface energy or quick mold release agent 12, e.g., silicone oil, fiuorohydrocarbon or fluorocarbon, such as Teflon, and the like. This, an optional but preferred step, facilitates removal of the cured composition or finished embossing member at the end of the process without damage.

(b) The pith-resin dry powder is then sprinkled or spread over the mold or matrix 10 to provide a layer 13 covering the pattern 11 to the desired depth.

The pattern and composition are then cold pressed, in an optional step, as between a pair of opposed platens (not shown), e.g., at 500 pounds per square inch pressure, and then (d) pressed between heated platens (not shown), e.g., at 300 F. for a period of eight minutes to yield an embossing or printing member 14 of, e.g., inch thickness.

(e) Both the matrix and the embossing or printing member 14 are then removed from the press (not shown), and the printing or embossing member 14 then separated from the matrix 10.

(f) The printing or embossing member 14 is then secured to a supporting screen or plate 15 and mounted upon a press platen 16 to form the face of an embossing platen.

The embossing platen 16 can then be mounted upon a conventional particleboard press ready for repetitive use in reproducing the original pattern, preferably after spraying with a quick release agent.

In mounting or securing the embossing member 14 to a supporting screen or plate 15, the members can be fastened conveniently by any one of the following methods: the members 14, 15 can be glued together; the plate 15 can be placed on top of the pith-resin composition just prior to the heating and curing step; or plate 15 can be embedded in the pith-resin composition as the latter is being springled upon the pattern 11. Subsequent hot pressing glues the members together.

It is apparent that the present invention is subject to various modifications and changes Without departing the spirit and scope of the invention.

Having described the invention, what is claimed is:

1. A process for forming an embossing structure by compressing and heating thermosetting materials within a mold providing a desired pattern to be reproduced, comprising the steps of forming a pith-resin composition by admixing bagasse pith with from about 5 percent to about 50 percent of a thermosetting resin, based on the total weight of pith and resin.

drying the said pith-resin composition to form a powder,

applying the dry powder to cover the pattern of the mold,

pressing and applying sufiicient heat and pressure to cure the powder,

and separating from the mold the cured member formed by powder bonding support.

2. The process of claim 1 wherein the applied pithresin composition comprises baggasse pith admixed with from about 5 percent to about 30 percent resin.

3. The process of claim 1 wherein the dry powder is spread over the pattern to be reproduced in concentrations ranging from about 0.10 to about pounds per square foot.

4. The process of claim 1 wherein the dry powder is pressed at temperatures ranging from about 250 F. to about 400 F., at a press time ranging from about three to about eight minutes.

5. The process of claim 1 wherein the dry powder is spread over the pattern to be reproduced after covering with a quick mold release agent.

6. The process of claim 1 wherein the dry powder is prepressed while cold, prior to the hot pressing and curing step.

7. The process of claim 6 wherein the dry powder is prepressed at pressures ranging from about 200 to about 1000 pounds per square inch.

References Cited UNITED STATES PATENTS 7/1965 Schafer 156245X 1/ 1969 Grandinetti et al. 156245X U.S. Cl. X.R. 

